全新java初学者实践教程6(Java SE5.0版)
,~ ?'Ef80 基本语法3
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"BW/%m|g 我们这个教程侧重的是实践的内容和语言的重点。在[font="Times]java语言中还有很多细节的东西,请参考[font="Times]sun公司的官方培训教程。我们这里不能一一讲述。这节课我们来给大家提供一些程序流程控制的一些例子供大家学习。计算机怎么做事情,是我们教给他的。我们用它解决实际生活中的问题,所以计算机要描述现实生活中的流程。[font="Times]Java语言中提供了[font="Times]4类程序控制语句,来描述流程:
@Un/c:n r#WT`pav [font="Times] 1.循环语句[font="Times]:while,do-while,for
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)BI:]m Y9SGRV( [font="Times]2.分支语句[font="Times]:if-else,switch,
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v/uO&iQw5 3.跳转语句[font="Times] break,continue,label: 和[font="Times]return
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`Yc_5&" 4.异常处理语句[font="Times]:try-catch-finally,throw
t{! F0~k1TDw 实践:
g1(Xg. [font="Times] 1.循环语句
JGiKBm; [font="Times] while 语句
+ww^ev% [font="Times]class While {
||2Q~*: [font="Times]public static void main(String args[]) {
hf!|\f [font="Times]int n = 10;
F}Mhs17!| [font="Times]while(n > 0) {
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DSfT{kK\ [font="Times]System.out.println("tick " + n);
,F+B Wot4 [font="Times]n--;
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xsl [font="Times]}
.=9s1~] [font="Times]}
Y izE5[* [font="Times]}
F9c`({6k [font="Times] do…while 语句
RnVtZ#SCh [font="Times] class DoWhile {
"re-@Baw [font="Times]public static void main(String args[]) {
Q^}%c
U0 [font="Times]int n = 10;
?<X(]I.j [font="Times]do {
TL= YQA [font="Times]System.out.println("tick " + n);
RKd [font="Times]n--;
CozKyt/r7 [font="Times]} while(n > 0);
W!$zXwY}( [font="Times]}
UbJ*'eoX [font="Times]}
vY6W|<s 二者区别,[font="Times]do…while至少循环一次,而[font="Times]while的表达式要是为[font="Times]flase的话可以一次也不循环。再通俗一点,[font="Times]do…while就算是括号里的是[font="Times]flase,人家最少也能[font="Times]do一次。
wbbqt0un [font="Times] for语句
hRaf# [font="Times] class ForTick {
l2v_?j-)x [font="Times]public static void main(String args[]) {
FHy76^h>e [font="Times]int n;
pvWau1ArNq [font="Times]for(n=10; n>0; n--)
Hyk'c't_O [font="Times]System.out.println("tick " + n);
;SwC&.I [font="Times]}
>Dm8m[76 [font="Times]}
?9j{V7h 与上面那两个的区别,[font="Times]for循环执行的次数是可以在执行之前确定的。通俗一点说吧,看这个例子[font="Times] for(n=10; n>0; n--)就是在括号里的时候,就已经知道要循环[font="Times]10次了。
&'|B =7 还有啊,[font="Times]for循环的部分可以为空的
78#!Q.## [font="Times]class ForVar {
;'T{li2 [font="Times]public static void main(String args[]) {
v|Jlf$> [font="Times]int i;
!Gs} tiMH [font="Times]boolean done = false;
4z7G2 [font="Times]i = 0;
Rz%e>) [font="Times]for( ; !done; ) {
R U"/2i [font="Times]System.out.println("i is " + i);
V|Tud [font="Times]if(i == 10) done = true;
]*"s\ix [font="Times]i++;
XY7Qa!>7j [font="Times]}
Ar9nBJ` [font="Times]}
[um&X=1V8 [font="Times]}
循环语句的例子下载 }m]q}r [font="Times] 2.分支语句[font="Times]
wWW~_zP0 [font="Times] if/else语句
Q.-*7h8 [font="Times]class IfElse {
*ck}|RhR [font="Times]public static void main(String args[]) {
YZ#V#[j'^ [font="Times]int month = 4; // April
H{ M)- [font="Times]String season;
`%K`gYhG1 [font="Times]if(month == 12 || month == 1 || month == 2)
_68BP)nz>. [font="Times]season = "Winter";
4Wel[] [font="Times]else if(month == 3 || month == 4 || month == 5)
U SOKDDm [font="Times]season = "Spring";
yFIy`9R [font="Times]else if(month == 6 || month == 7 || month == 8)
'aJgLws*w [font="Times]season = "Summer";
Lrz3 [font="Times]else if(month == 9 || month == 10 || month == 11)
`hh9"Ws% [font="Times]season = "Autumn";
XaI;2fMGI [font="Times]else
tgFJZA [font="Times]season = "Bogus Month";
$Ptk|qFe [font="Times]System.out.println("April is in the " + season + ".");
W+>wu%[L [font="Times]}
BW[5o3
i [font="Times]}
,#u\l>&$ [font="Times]//这段程序输出[font="Times]:
i`U:gw [font="Times]//April is in the Spring.
cH`^D?#se [font="Times]// 注意[font="Times] “[font="Times]||”是或运算
sOFa!bdPW [font="Times] switch语句
JXQPT [font="Times] class Switch {
}amU[U, [font="Times]public static void main(String args[]) {
;|ub!z9GG [font="Times]int month = 4;
>G)qns9 [font="Times]String season;
U)jUq_LX [font="Times]switch (month) {
_]#klL [font="Times]case 12:
Eyh|a.)- [font="Times]case 1:
8m=Z|"H@ [font="Times]case 2:
u4'z$>B [font="Times]season = "Winter";
*DeTqO65 [font="Times]break;
HB&
& [font="Times]case 3:
sLh0&R7 [font="Times]case 4:
Iq'O [font="Times]case 5:
x2wg^$F*oO [font="Times]season = "Spring";
X33v:9= [font="Times]break;
N{akg90 [font="Times]case 6:
<zB*'m [font="Times]case 7:
7Ur?ep [font="Times]case 8:
iv%w!3# [font="Times]season = "Summer";
`"y`AY/N [font="Times]break;
w8M2N]&: [font="Times]case 9:
SBKeb|H8 [font="Times]case 10:
y>o>WN<q [font="Times]case 11:
$%qg" [font="Times]season = "Autumn";
QEJGnl676 [font="Times]break;
E:A!wS`" [font="Times]default:
R"xp%:li [font="Times]season = "Bogus Month";
H3FW52pjX [font="Times]}
Z[#IfbYt [font="Times]System.out.println("April is in the " + season + ".");
;_JH:}j [font="Times]}
n[k1np$7?6 [font="Times]}
分支语句代码下载 ?T*";_o,B XF,<i1ZlM [font="Times]switch语句适合于条件非常多的逻辑
)q^ Bj$ 请看上述语句可以混合使用,请看
下载例子